Exposure controlling device for photographic camera

ABSTRACT

An exposure control circuit is caused to store a voltage representative of the light intensity of a selected principal object within the object field to be photographed by a manually operated member which disconnects a photosensitive element from a capacitive storage element. Operation of the manual member causes a switch interconnecting the photosensitive element with the capacitive storage element to be opened and a restraining member is provided for maintaining the switch in an opened condition until an exposure has been terminated. A cocking member operated in conjunction with the cocking of the camera causes the switch to be closed in preparation for another photograph.

United States Patent [191 Kuramoto et a1.

[ 1 Sept. 4, 1973 [73] Assignee: Minolta Camera Kabushiki,

Osaka-shi, Osaka-fu, Japan [22] Filed: June 4, 1971 [21] Appl. No.:149,938

[ 1 Foreign Application Priority Data June 4. 1970 Japan ..45/47553 [56]References Cited UNITED STATES PATENTS 10/1972 Mita 95/53 EB 2/1972 Ono95/10 CT 6/1967 Tsukamo Nobasama 95/10 CT 3,533,348 10/1970 Akio Yanagi95/10 CT X 3,349,678 10/1967 Minoru Suzuki et al. 95/10 CT 3,442,1905/1969 Erickson 95/10 CT Primary Examiner-Joseph F. PetersAtt0rneyWatson, Cole, Grindle & Watson [5 7] ABSTRACT An exposurecontrol circuit is caused to store a voltage representative of the lightintensity ofa selected principal object within the object field to bephotographed by a manually operated member which disconnects aphotosensitive element from a capacitive storage element. Operation ofthe manual member causes a switch interconnecting the photosensitiveelement with the capacitive storage element to be opened and arestraining member is provided for maintaining the switch in an openedcondition until an exposure has been terminated. A cocking memberoperated in conjunction with the cocking of the camera causes the switchto be closed in preparation for another photograph.

5 Claims, 4 Drawing Figures minnow 4 m5 IN OR YOSHI o KURAMOTO BYKAYOSHI TSUJIMOTO WATSON COLE GRINDLE & WATSON ATTOR YS PATENTED SE? 4SIEEIZBFS INVENTOR.

. YOSHIO KURAMOTO BY KAYOSHI TS UJIMOTO WATSON COLE GRINDLE & WATSONATTORNEYS PATENTl-Zflstr 4 ma FIG. 4

7* mW w 25 u 23 25b 28 INVENTOR.

YOSHIO KURAMOTO KAYOSHI TS UJIMOTO WATSON COLE GRINDLE & WATSONATTORNEYS EXPOSURE CONTROLLING DEVICE FOR PI-IOTOGRAPI-IIC CAMERABACKGROUND OF THE INVENTION The present invention relates to an exposurecontrolling device for a camera and more particularly to an exposurecontrolling device for controlling the exposure of electric shutter bymeasuring the light value of an objective field to bephotographed or aprincipal object in the objective field at a desired time prior toexposure to store the light deteched output.

The exposure controlling device for controlling the electromagnet in theelectric shutter by means'of the delay circuit composed of aphotoconductive element and a capacitor and the switching circuit arewell known, and it is also well known that in such an exposurecontrolling device a photosensitive element is arranged to effect a spotlight measurement for a specific portion in the objective field to bephotographed.

Further, it is also well known that in a single lens reflex camera formeasuring the light rays passing through the objective lens, the outputof the photosensitive element for measuring the light value of theobjective field just before exposure is stored by a storage capacitorand the exposure of the electric shutter is controlled in response tothe stored voltage of the storage capacitor.

In all such prior art apparatus, however, it is possible to measure thebrightness of a whole objective field to be photographed or a specificobjct in the whole objective field just before exposure or duringexposure but it is impossible to measure any object light in the wholeobjective field at any time before exposure and store the detected lightvalue thereof.

Therefore, the expsoure control can only be effected by the detectedlight value of the whole scene or a specific object in the whole scene.

This fact makes it impossible to measure the correct light value of, forexample, a desired object in the counterlight.

In order to measure correctly the light value for a desired object inthe objective field to be photographed the photosensitive element of thecamera may be brought close to an object before exposure to allow thephotosensitive element to measure only the light rays from the object,and storing the detatched value thereof to control the exposure inaccordance with the stored value for a desired photographic distance,and the proper exposure including good balance with the background ofthe object can be obtained.

OBJECTS OF THE INVENTION A primary object of the present invention is toprovide an exposure controlling device for a camera enabling the lightintensity of a specific object within an overall object field to bemeasured at any desired time prior to exposure.

A feature of the present invention is an exposure controlling device fora camera so constructed that a connecting switch for opening/closing alight measuring circuit and a capacitor for storing the signal outputthereof at a desired time before exposure are provided, and the exposureof the electric shutter is controlled in accordance with the signalstored by the capacitor.

Another feature of the present invention is that an RC integratingcircuit is operated simultaneously with the exposure and the integratedsignal and the measured lightintensity stored by a capacitor arecompared by a differential amplifier circuit. When both signals coincidewith each other the termination of the exposure is controlled inaccordance with the-light-intensity of any object in the objective fieldat-anytime'prior to exposure.

Still another feature of the present invention is'that an exposurecontrolling device for a single lens reflex camerais so constructed thatthe light passing through the objective lens is measured just prior toexposure and a signal representative thereof is stored by acapacitor andthe exposure control of the electric shutter is effected at the time ofthe subsequentexposure.

Other objects and features of the present invention will be apparentfrom the following detailed description taken in conjunction with theaccompanying figures.

SUMMARY OF THE INVENTION In order to attain the exposure controllingdevice of the above-mentioned objects the present invention is soconstructed that a photosensitive element for receiving the light raysfrom an object to be photographed is connected in parallel with acapacitor through a connecting switch, and after the output voltage ofthe photosensitive element is stored by the capacitor after closing theconnecting switch the output voltage is retained by the capacitor byopening the connecting switch. An RC integrating circuit is operatedsimultaneously with the release operation of a shutter mechanism and acomparison circuit compares the integrated output of the RC integratingcircuit with the output stored by the capacitor. When both outputscoincide with each other an electromagnet in a switching circuitterminates the exposure by closing the shutter mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of anembodiment in accordance with the present invention.

FIG. 2 is a circuit diagram of the control circuit for that embodiment.

FIG. 3 is a circuit diagram of another embodiment of the control circuitin accordance with the present invention.

FIG. 4 is a perspective view of the embodiment in accordance with thepresent invention wherein the components are cocked.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows the construction ofa camera shutter control mechanism, wherein the shutter is cocked priorto being released. Shutter button 1 shown in the left upper portion ofFIG. 1 is mounted slidably in shaft sleeve 42 of windinglever 41, andlower end la of shutter button 1 engages with left arm 2a of T-shapedconnecting rod 2 whichis vertically slidable relative to the camerabody.

Lower end 3a of longitudinal shaft 3 of T-shaped connecting rod 2engages with left end 5a of turning lever 5 which rotates around axis50.

Right end 5b of turning lever 5 engages with the flank of one arm 7a ofpreset lever 7 having a clockwise rotation tendency, namely, in thedirection shown from arrow CW by a spring not shown in the drawing aboutaxis 7c. When turning lever 5 and preset lever 7 are disengaged throughthe shutter release operation preset lever 7 is rotated in the directionshown by arrow CW to close main switch S (not shown in FIG. 1 but shownin FIG. 2) mounted in the turning track thereof, and at the same timeother arm 7b of preset lever 7 engages with one arm 8a of intermediatelever 8 rotatable about axis 8c to disengage other arm 8b from lower end11a of turning lever 11.

Turning lever 11 is provided fixedly on turning spindle 9a along withmovable reflection mirror 9 and has counter-clockwide turning tendency,namely, in the direction shown from arrow CW by a spring not shown inthe drawing, and when disengaged from the other arm 8b of intermediatelever 8 turning lever 11 turns reflection mirror 9 by means of thespring bias from a rest position at 45 with respect to the optical axisto a picture taking position parallel with the optical axis. And at thesame time, the other arm 11b of turning lever 11 engages with lower arm12a of S-shaped intermediate lever 12 about axis of rotation 12c to turnit clockwise.

Upper arm 12b of shaped lever 12 engages with one arm 13a of horizontallever 13 about axis of rotation 13c, so that the clockwise turning ofshaped lever 12 turns horizontal lever 13 counter-clockwise.

The other arm of horizontal lever 13 engages with restraining pawl 14aof restraining plate 14 mounted to turning spindle 15 to which openingscreen gear 16 is also mounted and that engagement can be broken throughthe counter-clockwise turning of horizontal lever 13.

Closing screen gear 25 is rotatably mounted above opening screen gear 16in an axial position to turning spindle 15.

Opening screen gear 16 is provided with two pins 16a, 16b projectingupward and closing screen gear 25 is provided with connection pin 25aprojected downward and restraining pin 25b projecting upward,respectively.

Restraining lever 23 has restraining arm 23a which enters and exits fromthe turning track of restraining pin 25b and is provided on the end ofthe other arm thereof with armature 23b facing electromagnet M.Restraining lever 23 has a clockwise turning tendency from spring bymeans of which armature 23b is separated from electromagnet M. Andcocking arm 22 is coaxially mounted with restraining lever 23. Cockingarm 22 is arranged so as to engage with pin 16b on opening screen gear16.

Shaft sleeve 42 is provided with winding lever 41 and windin g drivinggear 43, and supported rotatably about shutter button 1 on the camerabody. Winding driving gear 43 meshes with intermediate gear 44 supportedon the camera body and provided with two coaxial gears 46, 47 supportedby a pin on right arm 2b of T-shaped connecting rod 2. Gear 47 alwaysmeshes with intermediate gear 44 and gear 46 meshes with opening screengear 16 when T-shaped connecting rod 2 is in its uppermost position andis disengaged from opening screen gear 16 when T-shaped connecting rod 2is in its lowermost position obtained by the shutter release operation,thereby forming a clutch mechanism.

Further, open screen gear 16 meshes with gear 17 mounted to windingshaft 18 for opening screen 19and closing screen gear meshes with gear28 mounted to winding shaft 27 for closing screen 26. Opening andclosing screens 19, 26 are respectively wound, as well known, aroundtake up shaft 21 having a tendency to turn in the direction shown byarrow CW and closing screen take up shaft 29 has a tendency turn in thedirection shown by arrow CW,.

When winding lever 41 is turned clockwise, opening screen gear 16 isturned clockwise through gear train 43, 44 47, 46, and pin 16a ofopening screen gear 16 engages with connecting pin 25a so as to turnclosing screen gear 25 counterclockwise. Thereby opening and closingscreen gears 16, 25 respectively wind opening and closing screens 19, 26around winding shafts 18, 27, respectively, from take up shaft 21, 19.And, when the winding of the opening and closing screens is finishedrestraining pin 25b is turned to a position by pass ing throughrestraining arm 23a of restraining lever 23 which has rotated clockwiseby means of the tension of spring 20. Subsequently pin 16 engages withcharge arm 22 to turn it counterclockwise and accordingly turnrestraining lever 23 in the same direction, so as to contact armature23b with the pole of electromagnet M and confront restraining arm 23ainto the returning track of restraining pin 25b. Simultaneouslyrestraining pawl 14a of restraining plate 14 engages arm 13b ofhorizontal lever 13 and thus the cocking of the shutter is finished.

Closing screen winding shaft 27 has mounted on the lower end thereof camplate 31 having protrusion 31a, which is arranged to engage withprojection 34a on one arm of curved lever 34 having a counter-clockwiseturning tendency about axis 340 by spring 33. On the other end 34b ofcurved lever 34 pawl 34d is formed and is arranged to come into contactwith pin 36a fixed on one end of L-shaped lever 36 having a clockwiseturning tendency about axis 360 by spring 40. When pawl 34d engages withpin 36a it is restrained by L- shaped lever 36. On the other arm 36b ofL-shaped lever 36 there is fixed downwardly projecting pin 37 made of aninsulating material, and projection pin 37 faces contact piece 38 ofconnecting switch 8,. When L-shaped lever 36 rotates into clockwiseposition connecting switch S, is closed and when pin 36a of L- shapedlever 36 rotates into a counter-clockwise position engaging with pawl34d of curved lever 34 connecting switch S, is opened.

Button 39, one end 39a of which faces the flank of arm 36b of Lshapedlever 36, is supported slidably on the camera body and the other end 39bthereof protrudes outside of the camera body. By pushing end 39b button39 turns L-shaped lever 36 counter-clockwise against spring 40, opensconnecting switch 8,, and simultaneously as described above pin 36aengages with pawl 34d to hold connecting switch S, open.

In FIG. 2 electric power source E, photosensitive element R andtransistor T, are connected in series, and the base of transistor T, isconnected to the negative side of power source E through resistance R,.

The collector of transistor T, is connected to the base of transistor Tthrough connecting switch S, and condenser C,, for storing the measuredlight signal is connected to the negative side of power source E inparallel with photosensitive element R Power source E, main switch 8,,transistor T and electromagnet M are connected in series and the base oftransistor T, is connected to the collector of transistor T Triggerswitch S is connected in parallel with capacitor C and is openedsimultaneously with opening of the shutter and time constant resistanceR, is connected in series with both capacitor C, and switch S toconstitute an RC integrating circuit. And, the connecting point of timeconstant elements C,, R, is connected to the base of transistor TBetween emitters of transistors T, and T, common bias resistance R, isinserted, and the collector of transistor T, is connected to the base oftransistor T, as described above and to the positive side of powersource E through resistance R, and main switch 8,, so as to constitute adifferential amplifier circuit. When the charging voltage of time delaycapacitor C, coincides with the voltage stored by capacitor C,,transistors T T are made conductive and transistor T, is shut off.

Also, resistance R, can be a variable resistance varied in accordancewith the diaphragm setting and the film sensitivity setting, and in thismanner, after the measured light intensity is temporarily stored eventhough the diaphragm setting and the film sensitivity setting arechanged, exposure control can be effected.

Since the present invention is constructed as described hereinbefore, inthe objective field to be photographed when there is a remarkablecontrast in the brightness of the principal object, by bringing thecamera close to the object to allow the photosensitive element toreceive only the light rays from that object the light measurement iseffected, and in order to allow condenser C, to temporarily store thedetected light signal button 39 is pushed. And thus, L-shaped lever 36is turned counter-clockwise and insulating pin 37 thereof releasescontact piece 38 of connecting switch S, and accordingly connectingswitch S, is opened. Therefore, capacitor C, stores the detected lightoutput at that time. Further, pin 36a on the other end of L- shapedlever 36 engages with pawl 34d of curved lever 34 to be restrainedagainst spring 40 so as to keep connecting switch S, open.

At this juncture, if electrically connecting switch S, is closed, and inFIG. 2 the current of transistor T, is constant, so provided that thecollector current of transistor T, is i, the impedance of photosensitiveelement R, is r,, and the terminal voltage of photosensitive element isV,, V, i r,. That is, V, represents the meaured light value of theobject, and voltage V, is stored by capacitor C, when connecting switchS, is closed.

Thereupon, after setting a desired photographic distance to the objectand focusing, upon pushing shutter button 1 T-shaped connecting rod 2descends, turning lever 5 is turned counter-clockwise by longitudinalshaft 3, and preset lever 7 is released, so that preset lever 7 isturned in the direction shown by arrow CW to close main switch 8,.Simultaneously therewith, preset lever 7 engages with intermediate lever8 to turn it counter-clcokwise. And accordingly, intermediate lever 8and turning lever l 1 are disengaged and turning lever 11 is turned inthe direction shown by arrow CW, by means of its tendency to turnreflection mirror 9 to the picture-taking position.

Then, upper end 11b of turning lever 11 moves S- shaped lever 12 whichis thereby disengaged from horizontal lever 13 to release restrainingplate 14 mounted to turning spindle 15.

And at the same time, just as T-shaped connecting rod 2 descends, gear46 is released from engagement with opening screen gear 16, so thatopening screen gear 16 and turning spindle are driven via opening screen19 through the turning tendency of the opening screen take up shaft 21in the direction shown by arrow CW, to start the movement of openingscreen 19. And pin 16b releases cocking arm 22 and pin 16a is disengagedfrom connection pin 25a, however, in the electric circuit closed by mainswitch S, transistor T, is conductive and electromagnet M therebyexcited, so that restraining lever 23 engages with restraining pin 25bof closing screen gear 25 to prevent the latter gear from turning.

Just as opening screen 19 starts to move, as is well known, triggerswitch S is opened and delay capacitor C begins to be charged with thecurrent in accordance with resistance R,, and when the charging voltageof delay capacitor C, coincides with the detected light voltage storedby capacitor C, the output of the differential amplifier circuitswitches transistor T, non-conductive. Electromagnet M is demagnetizedto start closing screen 26 and thus the exposure is terminated. And atthe same time, on account of the turning of closing screen winding shaft27, cam plate 31 turns and protrusion 31a engages with projection 34a ofcurved lever 34 to turn curved lever 34 clockwise. Accordingly pawl 34dof curved lever 34 is disengaged from pin 36a of L-shaped lever 36 whichis turned clockwise by spring 40 to restore it to its original positionand thereby button 39 is restored to its original projecting position.

In contrast to the embodiment just described, in another embodimentshown in FIG. 3 switch 5, is inserted in series with connecting switchs, between photosensitive element R, and condenser C, for storing thedetected light voltage, and as long as connecting switch S, is closedswitch S, is closed so as to transfer the stored voltage to capacitor C,just prior to the turning of turning lever 11. Before turning lever 11is turned, switch S, is opened to allow condenser C, to store thevoltage, for example, switch S, is so constructed as to open and closein connection with the turning of preset lever 7 shown in FIG. I. Theother components are the same as those of the embodiment shown in FIG. 1and FIG. 2, and identical symbols denote identical parts.

FIG. 4 shows an embodiment using one switch S, for both connectingswitch S, and switch 8,, and the other components are the same as in theembodiment shown in FIG. 1 and FIG. 2, and identical symbols denoteidentical parts.

That is, FIG. 4 shows the condition wherein the shutter charge isfinished, and left arm 7b of preset lever 7 is able to engage with rightarm 8a of intermediate lever 8 in its turning track and to engage withpin 36a mounted on the one end of Lshaped lever 36.

And, under preset lever 7 there is provided lever 51 having hook 51a onits one arm which engages with pin 36a, and lever 51 has on its otherarm spring 52 for providing a counter-clockwise rotation about axis 51c.Pin 53 mounted on arm 51b is in the turning track of the right arm 7a ofpreset lever 7.

As to the photosensitive element, in FIG. 4 photoconductive element R,is provided on pentagonal prism P so as to measure light rays passingthrough the objective lens.

Therefore, when capacitor C, stores the detected light voltage of adesired object in theobjective field to be photographed, in the stateshown in FIG. 4, upon bringing the camera close to that object andpushing the button, connecting switch 8, is opened and pin 36a ofL-shaped lever 36 is restrained and its position is held against spring40. And, when controlling the exposure by storing the lightness of theobjective field just prior to exposure, upon performing the releaseoperation, just as connecting switch S, is left in the closing statepreset lever 7 is rotated to turn pin 36a of L- shaped lever 36 so as toengage it with pawl 34d in the same manner as described above. Thereby,connecting switch S, is opened to let capacitor C, store the detectedlight voltage. In any mode of photographing, as soon as the exposure isterminated cam plate 31 turns curved lever 34 to release the restrainteffected by pawl 34d, so that L-shaped lever 36 is returned to closeconnecting switch 5,, and simultaneously lever 51 is turnedcounter-clockwise by spring 52 and pin 53 thereof engages with presetlever 7 to push it to its original position.

Then, upon cocking the shutter by means of the winding lever, curvedlever 34 is turned clockwise and pawl 34d thereof engages with hook 51aof lever 51 to turn it clockwise against spring 52 to return it to theoriginal position shown in FIG. 4.

What is claimed is:

1. An exposure controlling device for a photographic camera comprising:

a photosensitive element for receiving light from a selected object withan object field to be photographed and generating an outputrepresentative thereof;

a capacitor for storing a voltage in accordance with said output;

first switch means for connecting said capacitor to said photosensitiveelement;

shutter exposure mechanism actuated by the camera shutter releasemechanism;

a shutter control circuit for controlling said shutter exposuremechanism to obtain an exposure in response to the stored voltage ofsaid capacitor; and

a manually operative means actuated independently of said shutterrelease mechanism solely for opening said first switch means prior to ashutter release operation.

2. An exposure controlling device as in claim 1, further comprising,means for preventing closure of said first switch means opened by saidmanually operative means.

3. An exposure controlling device as in claim 2 wherein said camerafurther comprises means for releasing said means for preventing closureof said first switch means interlocked with the operation of saidshutter exposure mechanism.

4. An exposure controlling device for a single lens reflex camera havinga movable reflector, comprising:

a photosensitive element for receiving light rays passing through theobjective lens of said camera and reflected by said movable reflector;

a capacitor for storing photometric data connected in parallel with saidphotosensitive element;

first switch means for connecting said capacitor to said photosensitiveelement;

a shutter control circuit for controlling an exposure in response to thevoltage stored by said capacitor;

a manually operative means for opening said first switch means prior toa shutter release operation;

a shutter release mechanism;

a second switch means serially connected with said first switch meansbetween said capacitor and said photosensitive element; and

means for automatically opening said second switch means before movementof said movable reflector in interlocking relationship with the startingof said shutter release mechanism.

5. An exposure controlling device for a single lens reflex camera havinga movable reflector, comprising:

a photosensitive element for receiving light rays passing through theobjective lens of said camera reflected from said movable reflector;

a capacitor for storing photometric data connected in parallel with saidphotosensitive element via a connecting switch;

a shutter control circuit responsive to the voltage charged on saidcapacitor;

a push button for manually opening said connecting switch; I

a means for automatically opening said connecting switch before movementof said movable reflector in interlocking relationship with the shutterrelease operation;

a member for restraining said connecting switch in the opening state;and

a means for releasing said restraining member in interlockingrelationship with the closing operation of the shutter.

1. An exposure controlling device for a photographic camera comprising:a photoseNsitive element for receiving light from a selected object withan object field to be photographed and generating an outputrepresentative thereof; a capacitor for storing a voltage in accordancewith said output; first switch means for connecting said capacitor tosaid photosensitive element; shutter exposure mechanism actuated by thecamera shutter release mechanism; a shutter control circuit forcontrolling said shutter exposure mechanism to obtain an exposure inresponse to the stored voltage of said capacitor; and a manuallyoperative means actuated independently of said shutter release mechanismsolely for opening said first switch means prior to a shutter releaseoperation.
 2. An exposure controlling device as in claim 1, furthercomprising, means for preventing closure of said first switch meansopened by said manually operative means.
 3. An exposure controllingdevice as in claim 2 wherein said camera further comprises means forreleasing said means for preventing closure of said first switch meansinterlocked with the operation of said shutter exposure mechanism.
 4. Anexposure controlling device for a single lens reflex camera having amovable reflector, comprising: a photosensitive element for receivinglight rays passing through the objective lens of said camera andreflected by said movable reflector; a capacitor for storing photometricdata connected in parallel with said photosensitive element; firstswitch means for connecting said capacitor to said photosensitiveelement; a shutter control circuit for controlling an exposure inresponse to the voltage stored by said capacitor; a manually operativemeans for opening said first switch means prior to a shutter releaseoperation; a shutter release mechanism; a second switch means seriallyconnected with said first switch means between said capacitor and saidphotosensitive element; and means for automatically opening said secondswitch means before movement of said movable reflector in interlockingrelationship with the starting of said shutter release mechanism.
 5. Anexposure controlling device for a single lens reflex camera having amovable reflector, comprising: a photosensitive element for receivinglight rays passing through the objective lens of said camera reflectedfrom said movable reflector; a capacitor for storing photometric dataconnected in parallel with said photosensitive element via a connectingswitch; a shutter control circuit responsive to the voltage charged onsaid capacitor; a push button for manually opening said connectingswitch; a means for automatically opening said connecting switch beforemovement of said movable reflector in interlocking relationship with theshutter release operation; a member for restraining said connectingswitch in the opening state; and a means for releasing said restrainingmember in interlocking relationship with the closing operation of theshutter.